Switching device



Dec. 30, 1941. A'. B.IMILLER 2,268,161

SWITCHING DEVICE Filed Dec. 12, 1939 Insulation.

HIS ATTORNEY Patented Dec. 30, 1941 UNITED STATES PATENT OFFICE SWITCHING DEVICE Application December 12, 1939, Serial No. 308,862

1 Claim.

My invention relates to electromagnetic switching devices, and particularly to electromagnetic relays suitable for use in centralized traflic controlling systems for railroads, such for example, as that disclosed in an application for Letters Patent of the United States, Serial No. 31,592, filed by Clarence S. Snavely and others on July 16, 1935, for Remote control systems.

One object of my invention is to reduce the amount of energy required to reliably operate a relay of the type described without in any way adversely affecting the stability of the relay and its contacts.

This object is attained in accordance with my invention by. operatively connecting the armature of the relay with the flexible contact fingers intermediate their ends and by causing each finger to cooperate only with a fixed front or a fixed back contact member so positioned that when the armature is in its mid-stroke position, each finger will be unstressed and will just touch the associated fixed front or back contact member. With this contact arrangement, the armature stroke necessary to provide the required contact compression and contact opening for both the front and back contacts is reduced to a minimum, which reduction in stroke decreases the length of the air gap which must be provided between the relay armature and the electromagnet pole pieces in the deenergized position of the armature. Any decrease in the length of the armature air gap for a given relay decreases the ampere turns required to reliably operate the armature to its attracted position, and since the energy consumed by an electromagnet varies as the square of the length of the air gap, it follows that the indicated contact arrangement appreciably decreases the amount of energy required to operate the relay.

Other objects and characteristic features of my invention will be made clear as the description proceeds.

A relay constructed in accordance with my invention is an improvement upon that described and claimed in Letters Patent of the United States No. 2,178,289, granted to Clarence S.

Snavely on October 31, 1939, for Electrical relays.

I shall describe one form of relay embodying my invention, and shall then point out the novel features thereof in claim.

The accompanying drawing is a front elevatype which is described in detail in the aforementioned Snavely Patent No. 2,178,289, and for a detailed description of the relay as a whole reference may be had to this patent wherein the same reference characters are used to designate the various parts as in the present application.

In general, the relay comprises a magnetizable armature ll disposed between the pole pieces 4 of an electromagnet A which is mounted on an insulating top plate B, and a pair of vertically spaced constantly magnetized auxiliary pole pieces I2 which are secured to the underside of the top plate B through the medium of an insulating supporting bracket II. The armature is moulded or otherwise secured to the upper end of a contact operating member I8 of suitable insulating material, and is adapted to be moved vertically, in response to energization of the electromagnet A, from a lower position in which its lower face engages a backstop Ila formed on a forwardly projecting tongue Hb comprising part of the bracket II, to an upper position in which its upper surface engages a pair of spaced depending front stops 2I formed on the underside of the top plate. The contact operating member I8 is guided in a manner to permit the necessary movement of the armature by means of a vertical guide rod 28 and a guide pin (not shown). The guide rod 28 is mounted at its upper end in an opening provided in the tongue 1 lb and at its lower end in an opening 3| provided in the lower end of a U-shaped contact support 22, and extends upwardly through aligned openings l8d provided in vertically spaced lugs 18b and I80 formed on the contact operating member l8. The contact support 22 is secured at its upper end to the underside of the top plate B in a manner not shown.

The contact mechanism of the relay, which contact mechanism embodies my present invention, comprises a plurality of vertically spaced superposed contact fingers 20 which are moulded into the opposite legs of the contact support 22 in such manner that alternate fingers are located in different legs and extend in opposite directions. These fingers extend intermediate their ends into slots |8f provided in the contact operating member l8, whereby they are operatively connected with the armature l1, and each cooperates at its free end with an associated fixed front contact member 23 or an associated fixed back contact member 24 to form a front contact 20-23 or a back contact 20-24 as the case may be, it being noted particularly that none of the fingers cooperates with both a front and a back contact member. The reason for this arrangeare each provided with contact buttons 25 of lowv resistance conducting material such as silver, which contact buttons cooperate with contact buttons 26, also of low resistance conducting material such as silver provided on the associated fixed contact members. The contact fingers and fixed contact members each extend through the associated legs of the contact support, and are provided with notched or pierced outer ends to facilitate making electrical connections with the fingers and fixed contact members.

The ampere turns required to operate a given relay vary directly with variations in the reluctance of the magnetic circuit. The reluctance of the magnetic circuit varies directly with its length. Since the air gap which must be provided between the armature and the pole pieces of theelectromagnet of a relay when the relay is deenergized forms a part of the magnetic circuit of the electromagnet, it follows that the reluctance of the magnetic circuit of a given relay, and, therefore, the ampere turns required to reliably operate the relay, decrease as the armature air gap is decreased. If the turns of the electromagnet are kept constant, then the current required to operatea given relay will vary directly as the open air gap. The energy consumed by an electromagnet varies as the square of the current, and it follows that the energy required to pick up the armature of a given relay varies directly as the square of the armature air gap. Therefore, anything that can be done to decrease the armature air gap will appreciably decrease the amount of the energy required to operate the relay.

For the purpose of reducing the armature air gap to a minimum, I so position the fixed front and back contact fingers with respect to the associated flexible contact fingers that when the armature is in its mid-stroke position, the fingers will be unfiexed and the contact buttons 25 on these fingers will just touch the contact buttons 26 on the associated fixed front and back contact members. With this arrangement, any downward movement of the armature from its midstroke position will cause the back contacts to start to become compressed simultaneously with the opening of the front contacts, whereas any upward movement of thearmature from its midstroke position will cause the front contacts to start to become compressed simultaneously with the opening of the back contacts. It follows,

therefore, that all parts of the movement of the armature between its two extreme positions is utilized either to provide contact compression or contact opening, and that no part of the stroke is utilized solely for the purpose of providing con- My present contact mechanism, however, possesses the advantage that it requires a minimum number of parts, and can be built into a smaller space than these other contact mechanisms. Furthermore, the parts can be moulded into place in a manner which requires substantially no adjustment during assembly, or at any subsequent time during the life of the relay. These features combine to reduce the cost of construction and,

maintenance of the relay which is very important in view of the large number of relays required in systems of the type for which the relay is designed.

Although I have herein shown and described only one form of an electromagnetic switching device embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claim without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is: 1

Switching means comprising an insulating supporting member having spaced parallel legs, a plurality of flexible contact fingers moulded into said legs in superposed parallel spaced relation in such manner that alternate fingers are located in different legs and extend in opposite directions, a plurality of rigid front and back contact members moulded into said legs and each cooperating with a difierent one of said fingers, each said frontor back contact member being disposed in the leg opposite to that in which the associated finger is moulded, and means for operating said fingers operatively connected with the fingers intermediate their ends, said fixed contact members being so positioned with respect to the associated flexible contact finger that when said operating means is in its mid-stroke position each finger will just touch the associated fixed contact member, whereby the stroke of said operating means necessary to operate said contacts is reduced to a minimum.

ALFRED B. MILLER. 

